Phytotaxa 184 (3): 131–138
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Copyright © 2014 Magnolia Press
Article
ISSN 1179-3155 (print edition)
PHYTOTAXA
ISSN 1179-3163 (online edition)
http://dx.doi.org/10.11646/phytotaxa.131.1.2
A new species of Mimosa (Leguminosae) from Brazil
LUCAS SÁ BARRETO JORDÃO1*, MARLI PIRES MORIM2 & JOSÉ FERNANDO ANDRADE BAUMGRATZ1,2
Museu Nacional/Universidade Federal do Estado do Rio de Janeiro, Rio de Janeiro, Brazil.
Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rio de Janeiro, Brazil.
*Author for correspondence: [email protected]
1
2
Abstract
A new species of Mimosa is described from the Atlantic Rainforest and ecotone with the Cerrado of southeastern Brazil, in
the states of Minas Gerais, Rio de Janeiro and São Paulo: M. porrecta L. Jordão, M.P. Morim & Baumgratz (Leguminosae).
Related to M. sensitiva, it shares morphological affinities with this species but differs in having porrect-stellate trichomes,
a new type of trichome for the genus, on the stems, and the dendritic trichomes in the fruits. The conservation status was
assessed, according to IUCN criteria, as Least Concern.
Key words: Mimosoideae; subserie Mimosa; taxonomy; trichomes
Introduction
Mimosa Linnaeus (1753: 516) (Leguminosae) is a monophyletic genus (Luckow et al. 2000, 2005, Bessega et al.
2008, Simon et al. 2011), and one of the largest genera of the family in Brazil. Simon et al. (2011) estimated about
536 species, but several new species have been described recently (Savassi-Coutinho et al. 2012, Dutra & Garcia
2013a,b,c, Morales et al. 2013; Santos-Silva & Tozzi 2012, Santos-Silva et al. 2013a, Grings & Ribas 2013).
Mimosa is pantropical, with its center of diversity in the Neotropics, and only 40 species in the Old World.
The species inhabit tropical, subtropical and dry forests, wetlands, grassland, restinga (sandy coastal-plain habitat),
savannas, prairies, and deserts. Many species are endemic, and it is believed that South America is the center of origin
of the genus (Barneby 1991, Simon et al. 2011). The main diversity and endemism centers are Mexico, the Brazilian
Cerrado, and subtropical South America (including areas of southern Brazil, Paraguay, Argentina and Uruguay), with
secondary centers in the Caribbean, Andes, Brazilian campos rupestres (montane savanna) and Madagascar (Barneby
1991, Grether et al. 1996, Simon & Proença 2000, Villiers 2002). According to Dutra & Morim (2014), 344 species
occur in Brazil.
The most recent taxonomic revision of Mimosa was conducted by Barneby (1991), who proposed a new
infrageneric classification. This treatment recognized 479 Neotropical species, in five sections (Batocaulon DC.,
Calothamnos Barneby, Habbasia DC., Mimadenia Barneby and Mimosa L.). However, molecular phylogenetic studies
have demonstrated that the sections are not monophyletic, with the exception of Mimadenia (Simon et al. 2011).
Although an extensive revision has been accomplished for Mimosa, several taxonomic complexities remain
unsolved, mainly because of the wide morphological variability and the large number of species. Several vegetative
and reproductive characteristics are diagnostic for Mimosa species. One of these is the indumentum, which has been
used to circumscribe the taxa because of the great diversity of trichome types (Barneby 1991, Santos-Silva et al.
2013b).
Recently, Jordão (2014) studied Mimosa in the Atlantic Domain in a region of southeastern Brazil, and recorded
38 taxa for this genus, among them a new species close to M. sensitiva. This new species is described here, and can be
identified based on a new trichome type, not yet reported for Mimosa; the inflorescence shape; and the morphology of
the calyx and fruit.
Accepted by Vidal Mansano: 16 Sep. 2014; published: 5 Nov. 2014
131
FIGURE 6. Inflorescence shape: conelike, in M. sensitiva var. sensitiva (A), and moriform, in M. sensitiva var. malitiosa (B) (A. D.
Araujo 452, RB; B. S.A. Mori s.n., RB 204966).
Characteristics of the fruit are also significant for taxonomy of Mimosa, as previously noted by Barneby (1991),
Dutra (2009) and Simon et al. (2011). The craspedium of M. porrecta differs from other related species in having the
epicarp densely covered with porrect-stellate trichomes, and the replum with dendritic trichomes.
IUCN Conservation assessment:—M. porrecta has a scandent shrubby habit. It occurs only in southeastern
Brazil, in the states of Minas Gerais, Rio de Janeiro and São Paulo (EOO=132,653 km², GeoCAT), in highland areas
of the Atlantic Forest and Cerrado domains between 650 and 1640 m altitude. It is common in disturbed sites, open and
pasture areas, and forest and roadsides. Although M. porrecta occurs in heavily human-impacted areas, it is also found
in several Conservation Units of Rio de Janeiro State, including Serra da Bocaina National Park, Serra dos Órgãos
National Park, Mata do Cedro Ecological Station, and Serra Nova State Park. This species is subject to ten threatening
situations considering the municipalities of occurrence. These factors support our assessment of the extinction risk for
M. porrecta as Least Concern (LC).
Acknowledgments
We are grateful for financial support from the Coordination for the Improvement of Higher-Education Personnel
(CAPES) for scholarships, and the support from the National Museum of Federal University of Rio de Janeiro
(UFRJ), the Rio de Janeiro Botanical Garden Research Institute (JBRJ) and the technicians of the Botanical Structural
Laboratory, Professors Claudia F. Barros and Karen L.G. Toni, and the curators of the above-mentioned herbaria.
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